Since gift is registered to you, you are sole owner of the property you can sale same to the person you wish. No buyer wont loose money you just take care of granny and regularly maintain her rest property can be sold.
Already the property is gifted to you vide registered deed you have full control over land , take care of granny regularly pay her medical expenses then her complaint under Senior citizen act wont be maintainable. There wont be any case of fraud or anything since you are true owner of the property,